Positioning is the process of geographically locating Mobile Stations (MS) in a Public Land Mobile Network (PLMN) by collecting and analyzing needed information, and after calculating the position, reporting it to an application for further usage.
Location-based services are forecasted to be an important feature in mobile communications network. A system for mobile positioning enables an operator to provide location-based services to its customers. Location information is an important enabler for many of the new services in the third generation mobile networks. Also, in some countries there are legal requirements on providing location information when an emergency call is made from an MS.
An ETSI standardised Gateway Mobile Location Centre (GMLC) discloses an example of a vital part of a mobile positioning system. The GMLC is the link between the PLMN and location services clients (LCS-C). It receives the positioning requests, performs the necessary authentication, initiates the positioning in the PLMN, and sends back the positioning information to the requesting application.
The knowledge of the location of a mobile entity opens up a new set of applications and enhances existing ones. A number of different applications in different fields, such as governmental, operators or commercial applications are and will be provided.
Each target group has its own demands and needs concerning location based services. Governmental use would typically be applicable for public welfare such as emergency calls and infrastructure planning. Operators have the ability for more accurate network planning by applying location information of large groups of mobile users. Commercial applications open up a whole new set of services.
Depending on the type of application it can be run either by an operator or a service provider. The operator is able to offer service providers access to location information, and the operator can also run its own applications. Existing services can be greatly enhanced and new services can be developed, with the knowledge of the geographical position of a mobile entity. The GMLC and a Serving Mobile Location Centre (SMLC)—which collects position information form the communications network and calculates the co-ordinates to be used by the application allows authorized applications, provided by the operator or third parties, to locate an MS using a variety of methods.
One important aspect of positioning is the support for location services (LCS) when mobile subscribers are roaming, i.e when a mobile subscriber is able to travel freely between cells while engaged in a single phone call, and international roaming, which means that the user can use the option of taking its phone abroad and using it in a Visited Public Land Mobile Network (VPLMN).
Another important aspect is that some applications, for example “friend-finder”-like applications, may need to obtain the position of MSs which are subscribers of other PLMNs.
Different PLMNs may support different location and roaming location mechanisms/protocols.
One such roaming location mechanism/protocol, known in the art, is used when the target MS is not located in its home PLMN (HPLMN) and SS7 signalling is used between the HPLMN and a VPLMN. In this mechanism the GMLC of the requesting LCS-C first interrogates the HLR (Home Location Register) in the home PLMN of the target MS for positioning routing information, i.e the current MSC/VLR (Mobile Switching Centre/Visitor Location Register) address of the MS. Then, this MSC/VLR is interrogated for positioning information. The MSC/VLR address can be located in any PLMN provided that it supports the same SS7 positioning roaming mechanism and that an SS7 roaming agreement exists.
Another approach for a roaming location mechanism/protocol is to use the Internet Protocol (IP). In this mechanism the GMLC of the LCS-C first interrogates the GMLC in the home PLMN of the target MS for positioning routing information, i.e in the PLMN where the MS is currently located. Then, the GMLC of this current PLMN is interrogated for positioning information. The MS can be located in any PLMN provided that it supports the same IP positioning roaming mechanism.
In addition to the above described methods, there also exist proprietary roaming support mechanisms and new proprietary solutions can be anticipated to evolve over time due to the consolidation of the number of PLMN operators.
Thus, there will probably exist various mechanisms/protocols and different operators and vendors will support these in various degrees. Further, when a positioning request is initiated it is not known which mechanisms will be needed during the course of the location procedure, since this will depend on in which PLMN the target MS is currently located, and the capabilities of that PLMN.
These state of the art solutions require that all PLMNs involved when positioning an MS must be able to support the same positioning roaming mechanism/protocol.
As set out above, it is anticipated that this will not be the case. Therefore, it is apparent that interoperability will be seriously jeopardized.
Also, it is anticipated that initiated but not successful positioning requests will create excess traffic load and thereby jeopardize system performance.